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91.
This paper presents the planar Fiber Bragg Grating (FBG) hydrophone probe sensing principle, and theoretically and experimentally researches the probe structure sensitivity, the receiving sensitivity frequency response characteristic and the acceleration response property. Planar sheet is made of stainless steel, its thickness is 0.15 mm, its diameter is 15mm, and the length of hollow circular shell is 20 mm. For this size of the structure, the probe structure sensitivity is up to 23 fm/Pa, which is about 7300 times of the value of the bare fiber. The resonance frequency is 6.5 kHz, and the amplitude-frequency curve of the receiving sensitivity response is relatively flat within the frequency range of 100 Hz to 5.5 kHz. The output yielded by one unit acceleration (1m/s2) is equivalent to (2.52 to 3.26 Pa) acoustic pressure acting output. This probe structure is easy to form FBG hydrophone array by multiplexing technique. The research shows that this planar structure not only can form FBG hydrophone probe, but also can constitute optical FBG laser hydrophone probe. The structure can realize different bandwidth, different range acoustic pressure measurement by adjusting the geometrical size of the sheet. 相似文献
92.
为了研究离子发动机羽流对航天器的影响,采用质点网格-蒙特卡罗碰撞方法对离子发动机羽流中的交换电荷离子进行了模拟。利用计算设备统一架构技术,开发出一套基于图形处理器的并行粒子模拟程序。随机数生成采用并行MT19937伪随机数生成器算法,电场方程使用完全近似存储格式的代数多重网格法求解。r-z轴对称坐标系中,在z=0 m处获得的电流密度均值为4.5×10-5 A/m2,图形处理器所得结果与中央处理器模拟结果吻合。在16核心的NVIDIA GeForce 9400 GT图形显示卡上,取得相对于Intel Core 2 E6300中央处理器4.5~10.0倍的加速比。 相似文献
93.
分析了影响风机盘管换热器传热性能的主要因素并提出相应的解决措施.采用理论分析与计算的方法,从提高传热效率出发对热交换器进行了改进.对于企业降低生产成本、提升产品性能和提高市场竞争力具有重要意义. 相似文献
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New commercial dosimetry systems need careful characterization and can benefit from the comparison with similar, in-house developed solutions. A comparison between such two dosimetry systems, both based on fibre-coupled organic plastic scintillator detectors, is presented. One system is the Exradin W1, fully commercialized by Standard Imaging, while the other system is the non-commercial ME40 system, developed by DTU Nutech with the aim of fundamental dosimetric research. Both systems employ plastic scintillator detectors that can be considered similar in design, calibrated using the same method, but differing primarily in the signal detection hardware. The two systems were compared with respect to essential dosimetric properties, with the purpose of testing their performance under conditions less well discussed in the literature. A Farmer ionization chamber was used as the primary reference of the comparison. The study demonstrated that the Cerenkov light ratio calibration coefficient of both systems was not constant, but changed systematically with photon beam quality to a maximum difference of 1.1%. Calibration with respect to stem effect correction should therefore be performed for every investigated beam quality when using plastic scintillator detectors. Both systems were found to be dose rate independent, even for the highest instantaneous dose rate evaluated (1.5 mGy per pulse). Low-dose measurements revealed large uncertainties for both systems, although the ME40 system handled short beam deliveries under reference conditions with accuracy and precision within 0.4%. Changes in response due to field size dependence were investigated and found to be as large as 3.3% for the W1 and 5.4% for the ME40, biasing output factor measurements in large fields. Great caution is therefore advised if using either system for measurements in large fields or under circumstances where the fibre irradiation geometry is unfavourable. Measurements of reference dose to water yielded differences up to 1.5% when compared with the Farmer ionization chamber for all investigated beam qualities. 相似文献
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Nikolaus KarpinskySong Zhang 《Optics and Lasers in Engineering》2012,50(2):280-286
We present a 3D video-encoding technique called Holovideo that is capable of encoding high-resolution 3D videos into standard 2D videos, and then decoding the 2D videos back into 3D rapidly without significant loss of quality. Due to the nature of the algorithm, 2D video compression such as JPEG encoding with QuickTime Run Length Encoding (QTRLE) can be applied with little quality loss, resulting in an effective way to store 3D video at very small file sizes. We found that under a compression ratio of 134:1, Holovideo to OBJ file format, the 3D geometry quality drops at a negligible level. Several sets of 3D videos were captured using a structured light scanner, compressed using the Holovideo codec, and then uncompressed and displayed to demonstrate the effectiveness of the codec. With the use of OpenGL Shaders (GLSL), the 3D video codec can encode and decode in realtime. We demonstrated that for a video size of 512×512, the decoding speed is 28 frames per second (FPS) with a laptop computer using an embedded NVIDIA GeForce 9400 m graphics processing unit (GPU). Encoding can be done with this same setup at 18 FPS, making this technology suitable for applications such as interactive 3D video games and 3D video conferencing. 相似文献
98.
在一台增压中冷的电控单体泵柴油机上采用柴油/甲醇组合燃烧(DMCC)方式进行排放特性与经济性试验研究。结果表明:采用DMCC方式能够大量减少NOx排放,同时CO2排放也有所降低。可以通过在排气管上加装氧化催化转换器(DOC)很好地清除掉DMCC方式增加的HC和CO排放,其催化效率在90%以上,比原机排放低很多,DMCC方式的甲醛排放比原机高,DOC对其催化率达98%,接近超低排放。DMCC模式外特性的热效率提高了7.607%,且存在一个最佳燃料匹配区间。 相似文献
99.
作者受厂家委托,对美国制造的《SZJ-10型沼泽检波器》的主要部件——《振荡探头》进行了有关技术参数的测试,测试结果基本符合实际,为生产厂家提供了测试方法和基本数据.本文《振荡钻探头》两个主要静态参数的测试方法做简单介绍。 相似文献
100.